A Thin Film Transistor Liquid Crystal Display (TFT-LCD) has characteristics such as small size, low power consumption and no radiation, and is prevailing in current market of flat panel display. The main structure of the TFT-LCD includes an array substrate and a color filter substrate that are cell-aligned, and a liquid crystal molecule layer filled between the array substrate and the color filter substrate. Based on different channel materials, TFTs in the prior art mainly includes two kinds, i.e., oxide semiconductor TFT (abbreviated as oxide TFT) and amorphous silicon TFT. The oxide TFT is more suitable for manufacturing high-end display products with high resolution (high definition) and high refresh rate (smoother motion graphics), because the oxide TFT has characteristics of a larger on-off current ratio, i.e., when it is turned on, the current is larger and the charging time is shorter; and when it is turned off, the leakage current is smaller and leakage is not easy to occur).
FIG. 1 is a structural schematic diagram of a typical oxide TFT. The oxide TFT comprises: a substrate 1, a gate electrode 2 formed on the substrate 1, a gate insulating layer 3 formed over the gate electrode 2, an active layer 4 formed over the gate insulating layer 3, source and drain electrodes 6a and 6b and an etching barrier layer 5 formed over the active layer 4 and the gate insulating layer 3, a passivation layer 7 formed over the source electrode and drain electrode 6a and 6b, and a pixel electrode 8 formed over the passivation layer 7, the pixel electrode 8 being connected with the drain electrode 6b through a via hole in the passivation layer 7. Such a structure has a problem that, in order to improve the response speed of the oxide TFT, it is necessary to use a metal having a relatively high electrical conductivity as the source and drain electrodes, while diffusion ability of conductive particles in the metal having a relatively high electrical conductivity is strong and the conductive particles may easily diffuse into the oxide active layer 4 and affect the electrical performance of the oxide active layer 4. When such an oxide TFT is used in a display product, it will affect the display performance of the corresponding display product.